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Form 4 Physics Floating and Sinking Questions and Answers

In this session, we are going to solve floating and sinking questions for Physics Form 4.

Lessons (24)

• 1.    A solid copper sphere will sink in water while a hollow copper sphere of the same mass may float. Explain this observation
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• 2.    A concrete block of volume V is totally immersed in sea water of density #rho# . Write an expression for the upthrust on the block.
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• 3.    Figure 7 represents a block of uniform cross sectional area of #6.0cm^2# floating on two liquids A and B.The lengths of the block in each liquid are as shown. Given that the density of liquid A is #800kgm^-3# and that of liquid B is #1000kgm^-3#, determine the: i. Weight of the liquid A displaced ii. Weight of the liquid B displaced(2marks) iii. Density of the block(4marks)
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• 4.    Figure 2 shows a uniform bar in equilibrium. When water is added into the beakers A and B until the weights are submerged, it is observed that the bar tips towards B. Explain the observation.
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• 5.    Figure 19 shows two spheres made of wax each of mass 0.10kg held in a liquids by strings A and B. If the up thrust on each sphere is 1.05N, determine the tension in each string. (acceleration due to gravity g =#10ms^-2#) (3marks)
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• 6.    A block of glass of mass 250g floats in mercury. What volume of glass lies under the surface of the mercury? (Density of the mercury is 13.6×#10^3kgm^-3#). (3marks)
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• 7.    When a piece of metal is placed on water, it sinks. But when the same piece of metal is placed on a block of wood, both are found to float. Explain this observation.
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• 8.    The system in Figure 2 is in equilibrium at room temperature. The system is taken outside where the temperature is #10^0C# higher for some time. Explain why this tips to the right immediately it is returned to the room.
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• 9.    a) A test tube of uniform cross section is loaded so that it can float upright in water.With an aid of a labelled diagram, describe how the test tube may be calibrated to measure the density of liquid b) In an experiment to determine the density of a liquid, a uniform metal cylinder of cross section- sectional area #6.2cm^2# and length 4.5cm was hang from a spring balance and lowered gradually
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• 10.    The uniform bar in Figure 7 is pivoted at its midpoint. It is in equilibrium under the action of two identical balloons filled with equal volumes of different light gases at the same temperature. Explain why the bar may not remain in equilibrium if the temperature of the surrounding changes.
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• 11.    (a) State Archimedes principle (b) In an experiment to determine the relative density of the methylated spirit applying Archimedes principle, the following were provided: a spring balance, some masses, a piece of thread, water in a beaker and methylated spirit in a beaker. The table below shows the results obtained. (i) Draw labeled sketch diagrams to show how the readings in the table were
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• 12.    (a) State the law of floatation (b) Figure 13 shows a simple hydrometer. (i) State the purpose of the lead shots in the glass bulb (ii) How would the hydrometer be made more sensitive? (iii) Describe how the hydrometer is calibrated to measure relative density. (c) Figure 14 shows a cork floating on water and held to the bottom of the beaker by a thin thread. (i) Name the forces acting on the cork
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• 13.    The system in figure 8 is in equilibrium When the temperature of the water is raised the system is observed to tilt to the right. State the reason for this observation.
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• 14.    (a) Figure 10 shows a rectangular metal block of density #10500kgm^-3# and dimensions 30cm ×20cm×20cm suspended inside a liquid of density #1200kgm^-3# by a string attached to a point above the liquid. The three forces acting on the block are the tension T, on the string, the weight W of the block and the upthrust U due to the liquid. (i) Write the expression relating to T, W and U when the block
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• 15.    The weight of a solid in air is 5.0N. when it is fully immersed in a liquid of density #800kgm^-3# , its weight is 4.04N. Determine: (a) The upthrust in the liquid. (b) The volume of the solid.
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• 16.    Figure 8 shows stone of mass 4.0kg immersed in water and suspended from a spring balance with a string. The beaker was placed on a compression balance whose reading was 85N. The density of the stone was 3000#kgm^-3# while the density of the liquid was 800#kgm^-3# Determine the: (a)volume of the liquid displaced. (b) upthrust on the stone (c) reading of the spring balance (d)reading of the compress
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• 17.    (a) State the condition necessary for a body to float in a fluid. (b) A ship made of steel is observed to float on water yet the density of steel is approximately eight times that of water. Explain this observation. (c) Figure 17 shows three stages of an experiment to determine relative density of cork which normally floats on water. To make a sinker hang below the cork. In (I) a spring balance is
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• 18.    A balloon is filled with a gas which is lighter than air. It is observed to rise in air up to a certain height. State a reason why the balloon stops rising.
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• 19.    Figure 13 shows a log of wood of mass 20kg submerged in water in a pond and held in position by string fixed to the bottom of the pond. Given that the density of water is 1000#kgm^-3# and that of wood is 800#kgm^-3#, determine the; (i) Volume of the log (ii) Upthrust of the log (iii) Tension in the string
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• 20.    (a) Figure 12 shows a weighing balance on which a beaker containing some water is placed. The reading on the balance is 2.80N. A metal block weighing 2.7N is suspended from a spring balance. (i) State what is observed on the spring balance and the weighing balance, as the metal block gradually lowered into the water. (I) Observation on spring balance. (II) Observation on weighing balance.
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• 21.    Figure 11 shows a test- tube whose cross-sectional area is 2#cm^2# partially filled with lead shot floating vertically in water. (Take gravitational acceleration as 10#ms^-2# and density of water ??w, as 1 g# cm^-3#) (a) (i) Determine the: I volume of the water displaced II weight of the water displaced (ii) State the combined weight of the test-tube and the lead shot (iii) Determine the length of
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• 22.    (a) Figure 6 shows two solids W and X made of the same material and immersed in water. (i) State with a reason one of the containers experiences a greater upthrust. (ii) Solid W weighs 12N in air, 2N in water and 4N in another liquid. Determine the density of the other liquid. (b) Figure 7 shows two identical wooden blocks each of mass 0.2kg suspended in water by two strings M and N. Given that
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• 23.    A wooden cube of side 0.5m floats in water fully submerged. Determine the weight of the cube. (Density of water=1#gcm^-3#)
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• 24.    A stone of volume 800#cm^3# experiences an upthrust of 6.5N when fully immersed in a certain liquid. Determine the density of the liquid.
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